1. Field of the Invention
The present invention generally relates to an image display system and manufacturing method thereof, and more particularly to an AMOLED (Active Matrix Organic Light Emitting Diode) circuit and manufacturing method thereof.
2. Description of Prior Art
An OLED (Organic Light Emitting Diode) display is generally acknowledged as the next generation technology for the flat panel display, in which an AMOLED (Active Matrix Organic Light Emitting Diode) display is especially concerned. The related manufacturing industries are committing enormous resources to develop such AMOLED products. A pixel unit of the AMOLED display includes a driving TFT (Thin Film Transistor), a switching TFT, a luminous element (i.e. OLED element) and a capacitor. As manufacturing the aforesaid elements of the AMOLED, an ELA (Excimer Laser Anneal) is employed to transform an amorphous silicon layer into a poly silicon layer.
Different demands of electrical characteristics exist for the driving TFT of a driving circuit for driving the luminous element (e.g. OLED element) and the switching TFT. For example, A high mobility is preferred for the switching TFT while the driving TFT is preferred to have a small crystal grain size so as to reduce discrepancies among the respective luminous elements (OLED elements), that is, to reduce the mura issue caused by the non-uniformity among transistors. Therefore, it is preferable that the poly silicon layers having different crystal grain characteristics are formed on different areas during the crystallization processes of transforming the aforesaid amorphous silicon layer into the poly silicon layers.
In related manufacturing industries today, different crystallizations in different processes are now being utilized to achieve the aforesaid objective. For example, a laser crystallization process such as ELA (Excimer Laser Anneal) and a non-laser crystallization process such as SPC (Solid Phase Crystallization), MIC (Metal Induced Crystallization), MILC (Metal Induced Lateral Crystallization), FE-MILC (Field Enhanced Metal Induced Lateral Crystallization), or the like can be used.
However, the method of employing the aforesaid different crystallizations in the different processes takes more time and is quite complicated in comparison to a single laser crystallization process. Therefore, it is still difficult to increase the yield. Moreover, the poly silicon layers formed by aforesaid different crystallization processes show apparent discrepancies of the crystal grain characteristics. The present invention is intended to solve the low yield problem of the AMOLED products because of the mura issue caused by the discrepancies among the respective luminous elements (OLED elements).